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Annotation of 43BSD/sys/vax/ufs_machdep.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1982, 1986 Regents of the University of California.
        !             3:  * All rights reserved.  The Berkeley software License Agreement
        !             4:  * specifies the terms and conditions for redistribution.
        !             5:  *
        !             6:  *     @(#)ufs_machdep.c       7.1 (Berkeley) 6/5/86
        !             7:  */
        !             8: 
        !             9: #include "pte.h"
        !            10: 
        !            11: #include "param.h"
        !            12: #include "systm.h"
        !            13: #include "dir.h"
        !            14: #include "user.h"
        !            15: #include "buf.h"
        !            16: #include "conf.h"
        !            17: #include "proc.h"
        !            18: #include "seg.h"
        !            19: #include "vm.h"
        !            20: 
        !            21: /*
        !            22:  * Machine dependent handling of the buffer cache.
        !            23:  */
        !            24: 
        !            25: /*
        !            26:  * Expand or contract the actual memory allocated to a buffer.
        !            27:  * If no memory is available, release buffer and take error exit
        !            28:  */
        !            29: allocbuf(tp, size)
        !            30:        register struct buf *tp;
        !            31:        int size;
        !            32: {
        !            33:        register struct buf *bp, *ep;
        !            34:        int sizealloc, take;
        !            35: 
        !            36:        sizealloc = roundup(size, CLBYTES);
        !            37:        /*
        !            38:         * Buffer size does not change
        !            39:         */
        !            40:        if (sizealloc == tp->b_bufsize)
        !            41:                goto out;
        !            42:        /*
        !            43:         * Buffer size is shrinking.
        !            44:         * Place excess space in a buffer header taken from the
        !            45:         * BQ_EMPTY buffer list and placed on the "most free" list.
        !            46:         * If no extra buffer headers are available, leave the
        !            47:         * extra space in the present buffer.
        !            48:         */
        !            49:        if (sizealloc < tp->b_bufsize) {
        !            50:                ep = bfreelist[BQ_EMPTY].av_forw;
        !            51:                if (ep == &bfreelist[BQ_EMPTY])
        !            52:                        goto out;
        !            53:                notavail(ep);
        !            54:                pagemove(tp->b_un.b_addr + sizealloc, ep->b_un.b_addr,
        !            55:                    (int)tp->b_bufsize - sizealloc);
        !            56:                ep->b_bufsize = tp->b_bufsize - sizealloc;
        !            57:                tp->b_bufsize = sizealloc;
        !            58:                ep->b_flags |= B_INVAL;
        !            59:                ep->b_bcount = 0;
        !            60:                brelse(ep);
        !            61:                goto out;
        !            62:        }
        !            63:        /*
        !            64:         * More buffer space is needed. Get it out of buffers on
        !            65:         * the "most free" list, placing the empty headers on the
        !            66:         * BQ_EMPTY buffer header list.
        !            67:         */
        !            68:        while (tp->b_bufsize < sizealloc) {
        !            69:                take = sizealloc - tp->b_bufsize;
        !            70:                bp = getnewbuf();
        !            71:                if (take >= bp->b_bufsize)
        !            72:                        take = bp->b_bufsize;
        !            73:                pagemove(&bp->b_un.b_addr[bp->b_bufsize - take],
        !            74:                    &tp->b_un.b_addr[tp->b_bufsize], take);
        !            75:                tp->b_bufsize += take;
        !            76:                bp->b_bufsize = bp->b_bufsize - take;
        !            77:                if (bp->b_bcount > bp->b_bufsize)
        !            78:                        bp->b_bcount = bp->b_bufsize;
        !            79:                if (bp->b_bufsize <= 0) {
        !            80:                        bremhash(bp);
        !            81:                        binshash(bp, &bfreelist[BQ_EMPTY]);
        !            82:                        bp->b_dev = (dev_t)NODEV;
        !            83:                        bp->b_error = 0;
        !            84:                        bp->b_flags |= B_INVAL;
        !            85:                }
        !            86:                brelse(bp);
        !            87:        }
        !            88: out:
        !            89:        tp->b_bcount = size;
        !            90:        return (1);
        !            91: }
        !            92: 
        !            93: /*
        !            94:  * Release space associated with a buffer.
        !            95:  */
        !            96: bfree(bp)
        !            97:        struct buf *bp;
        !            98: {
        !            99: 
        !           100:        bp->b_bcount = 0;
        !           101: }

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